Considering the effect of non-uniform critical current density of high-temperature superconductors and AC loss of flux jump theory

Title: Considering the effect of non-uniform critical current density of high-temperature superconductors and AC loss of flux jump theory Author: Zhao Yufeng Degree-granting units: Lanzhou University Keywords: high-temperature superconducting material;; flux jump;; AC losses;; high-temperature superconducting thin films;; non-uniform distribution of critical current density effect;; Bean model;; Kim model;; flux dynamics;; transmission loss ;; magnetization loss;; hysteresis loop;; magnetic thermal instability;; Norris equation;; Maxwell equations Abstract:
High-temperature superconductors at very Magnetic lifter low temperature environment of the flux jump instability phenomena and conditions in effect under alternating energy loss is directly related to the superconducting device and system security and stability, superconductor applications are the fundamental issues of concern His research has been highly valued. As the high-temperature superconducting materials in the preparation process there is inevitably a large number of various types of lattice defects caused by the pinning potential within the superconductor critical current density and uneven distribution, then the associated loss of flux jumps and exchanges become Superconducting devices and systems security design and optimization of key scientific issues. In this paper, the local magnetic thermal insulation is assumed from the perspective of the interaction of non-uniform distribution of critical current density effect on the flux jumps and the impact of exchange losses and high-temperature superconducting thin films of magnetic field and current density distribution and loss of in-depth study , and obtained some meaningful results.
First, for high-temperature superconductors the critical current density of magnetic flux jumps non-uniform distribution of effects, from the perspective of the magnetic interaction of environmental hot initial rate of change of temperature and magnetic field effects by solving the first flux jump prediction equation established a critical flux jump effects of non-uniform distribution of current density the theoretical model, while the critical state theory in the context in which heat distribution and temperature response shows high-temperature superconductors magnetic flux jumping resolution representation. In this paper, the theoretical model can predict the existing experimental data and numerical results and theoretical calculations found: non-uniform distribution of the critical current density effects seriously affect the flux jump phenomenon, the generation of magnetic flux jumps are inhibited, http://www.999magnet.com/products/131-magnetic-lifter and with the the characterization of the critical current density in different regions of the parameters intensity difference γ = J_ (cw) / J_ (cs) increases, the inhibition becomes more significant.
Second, consider the self-field equations based on the role of Norris, the critical current density analysis of the effects of non-uniform distribution of high-temperature superconducting wire transfer cylinder exchange loss of influence. Calculated that: superconducting critical current density along the wire cylinder radial increments from the inside and outside the non-uniform way to effectively reduce the transmission loss. When the normalized transport current is larger or close to the critical current, critical current density of the non-uniform effect on the transmission loss of more significant; when the normalized transport current is small, its impact under normal circumstances is negligible. Critical current density along the radial cross-section from the inside and outside the square a linear way and loss of behavioral change and to step-like way different. In particular, cylindrical cross section of superconducting critical current density at the boundary of the distribution is extremely important for reducing the transmission loss.
Finally, consider the two-dimensional high-temperature superconducting thin film superconductivity and magnetic field effects and the distribution of current density characteristics of the AC losses of superconducting thin films non-uniform distribution of critical current density effect. Calculated that: flat and thin-film superconducting samples of external applied magnetic field and transport current of the electromagnetic response is essentially the difference. Strong magnetic field, respectively, linear and nonlinear superconducting plate in the form of penetrating and film. No flat field in the superconducting region is zero and the critical current density to J_c transport current in the film critical current density of J_c field area in the non-zero and not its continuous change. Film transmission loss of the critical current density on the qualitative effect of non-uniform distribution of geometric shapes with other superconductors are basically the same, when the film magnetization in the high field critical current density loss of non-uniform effects gradually disappear.
In short, through this paper, high-temperature superconducting materials, AC losses of the flux jump and the critical current density non-uniform distribution of effects research, and correctly predict the accurate measurement of field flux jump occurs, the exchange loss and other performance parameters provide a good theoretical basis, and this study of high-temperature superconducting devices and high-temperature superconducting thin film devices for accurate design and application of great significance.